On what grounds did nixon refuse to turn over tapes during his presidential scandal?

Nixon refused to turn over the tapes during his presidential scandal under the grounds of "the right to privacy" protected by the 4th amendment. However, the 4th amendment didn't apply to him, because he was the leader of the US, and the citizens have a right to know what is going on inside the White House, as decision made in there can affect the people of US.

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